A comparative study of four coronal obturation materials in endodontic treatment.

The aim of this study was to compare, in vitro, the ability of temporary versus permanent materials to seal the access cavity. Eighty human maxillary single-canal teeth were prepared biomechanically and obturated with gutta-percha and an endodontic cement AH Plus, using the warm vertical compaction technique. All access cavities were sealed with 1 of 4 materials (Cavit, Fermit, Tetric, or Dyract). Microleakage was assessed by methylene blue dye penetration. The teeth were submitted to 100 thermocycles, with temperature varying from 0 degree to 55 degrees C. The greatest degree of leakage was observed with the temporary materials (Cavit and Fermit). There was a significant difference (p < 0.05) in leakage between all materials except between Dyract and Tetric. This suggests that it may be more prudent to use a permanent restorative material for provisional restorations to prevent inadequate canal sealing and the resulting risk of fluid penetration.

Effect of masticatory cycles on apical leakage of obturated teeth.

This study investigated the effect of apical leakage due to masticatory cycles on root canal treatment. Twenty upper maxillary molars were first obturated using the warm vertical compaction technique. Four maxillary casts were then built, with each holding four of the sample molars. The molars were embedded in resin with the roots separated from the resin by means of a light silicon. The four remaining teeth served as controls and were not submitted to occlusal forces. A mechanical device to simulate masticatory cycles subjected the teeth to 0.5 x 10(6) cycles (group A), 10(6) cycles (group B), 2 x 10(6) cycles (group C), and 3 x 10(6) cycles (group D); the control was group E. The roots were placed in 2% methylene blue dye solution for 72 h and then sectioned longitudinally so that dye penetration could be measured. The mean values of dye penetration were: 3.70 +/- 0.69 mm, group A; 5.00 +/- 1.14 mm, group B; 6.00 +/- 1.01 mm, group C; 7.23 +/- 0.66 mm, group D; and 2.74 +/- 0.75 mm, group E. The value of dye penetration increased in correlation with the number of masticatory cycles. This in vitro study suggests the significant effect of masticatory loads on apical leakage.

Warm vertical compaction sequences in relation to gutta-percha temperature.

The aim of this study was to analyze warm vertical compaction sequences in relation to the temperature variations of gutta-percha. Twenty-four maxillary incisors were obturated according to two different instrumentation techniques: Compaction and heating were performed with either the monomanual classical or bimanual method. To evaluate gutta-percha temperature, thermocouples (TC) were introduced into channels bored through the dentin into the root canal system or fixed on the root surface at 8 (TC8), 4 (TC4), 2 (TC2), and 0 mm (TC0) from the apex. Maximal temperature was 118 degrees C for TC8, 52 degrees C for TC4, and 44 degrees C for TC2 and TC0. At TC0, the temperature remained above 42.9 degrees C for 10 +/- 5 s. These results show the importance of heating down to a distance of 7 mm to ensure a significant increase in apical gutta-percha temperature. They further indicate that the last compaction should last more than 15 s to avoid detrimental cooling and dimensional variations. The principal differences between the monomanual and bimanual methods were the compaction time (5.07 +/- 0.2 min vs 4.02 +/- 0.3 min) and the number of compactions (8 +/- 1 vs 12 +/- 2).

Analysis of the forces developed during obturation: warm vertical compaction.

The aim of this work was to measure and analyze the forces applied by endodontists during an obturation. This was achieved by devising a system of force transducers linked to acquisition software. The software allowed us to study the obturation forces in real time or to store them. In this initial study, the forces developed by endodontists and students during a warm vertical compaction were analyzed. The vertical and frontware backware horizontal direction forces were first stored. Graphs of the compaction forces were then generated, permitting the analysis of the obturation method. Indeed, two cases of obturation failure were analyzed from these graphs. The mean values for the vertical forces applied by the endodontists and students were, respectively, 2.5 +/- 0.4 kg and 1.9 +/- 0.9 kg; the mean values for the lateral forces were, respectively, 0.85 +/- 0.2 kg and 1.4 +/- 0.6 kg. This device permits the analysis of compaction forces and may thus be highly useful in obtaining improvements in obturation techniques.

Effect of masticatory cycles on tooth compression and resultant leakage of amalgam retrofills.

This study was carried out to investigate the effect of changes in tooth structure due to masticatory cycles on amalgam retrofillings performed to different cavity depths. Forty upper maxillary first molars were tested. In the obturated palatal root apical amalgam was inserted to different depths (1.5 and 3 mm). Eight casts were built, each having four sample molars. To block the teeth, the vestibular roots were embedded in resin (palatal root was left free). The eight remaining retrofilled teeth served as controls and were not submitted to occlusal forces. A mechanical device to simulate masticatory cycles subjected the teeth to 500,000 to three million cycles. Leakage was assessed from dye penetration observations. The values of microleakage were analyzed and compared, and strain gauges were used to assess structural modifications to the tooth. The leakage of all retrofilled obturations increased in correlation with the number of masticatory cycles. At three million cycles, root length compression was 0.3 +/- 0.02%. Leakage was significantly less for the deeper cavity preparations at all stages. This in vitro study suggests a significant effect by root compression due to masticatory loads on the leakage of retrofilled amalgam obturations.